The present invention relates to a leakage current interruptor, particularly to an improved electrical ground fault receptacle assembly for protecting electric appliances from the hazards of ground fault currents by operation of a ground fault interrupting circuit.
Conventional receptacle structures employ a mechanism of a type which utilizes the electric characteristics of bimetal and solenoid to interrupt ground fault current upon occurence of ground fault. But such mechanisms have a disadvantage because ground faults can not be instantly interrupted. Thus, in the event of a short circuit or other overcurrent abnormalities, the safety of an electric appliance is not completely guaranteed.
Also, to overcome the above disadvantage, U.S. Pat. No. 4,084,203 issued to Robert E. D. Dietz etc. on Apr. 11, 1975, shows a receptacle assembly provided with a ground fault circuit interrupter having the size of an ordinary household or commercial junction box. This receptacle assembly comprises a ground fault detecting circuit for sensing a ground fault, and a coil and a trip mechanism for separating a protection circuit from the power supply whenever a ground fault occurs. This receptacle assembly was constructed so that the ground fault detecting circuit includes two differential transformers to sense a low level ground fault upon occurance of a ground fault, and to feed the ground fault detecting signal to an amplifier, and then to trigger a switching device by means of the amplified signal, thereby preventing damage of an electric appliances by ground fault.
The trip mechanism installed in this receptacle assembly is comprised so that the carrier member and the armature be coordinated with each other as a independent mechanism spaced away from the trip coil.
But, when the trip mechanism is activated to open the protecting circuit on the occurance of a ground fault, it does not instantly interrupt because the shut-off of excess current depends on the operation and interaction of numerous steps, for example, the arrangement of the coil and the armature, the arrangement of the armature and the carrier, the arrangement of the carrier and the reset switch, and the arrangement of the reset switch and the ring. The interaction of each operating component has a tendency to delay the overall function, resulting in less than complete protection of electric appliances. This is especially true since the trip mechanism is very complex in construction.
Thus, the present invention is devised so that the ground fault detecting circuit is activated by a minimum sensing current of the ground fault signal allowing the trip mechanism to instantly interrupt the ground fault current, thereby providing protection to electric appliances.